一封英文信件看不太懂是否有高手可以翻譯一下?

我在國外有買一件東西可是以經過二個多星期了還沒收到，有寫了一封信件過去，對方回我如下面，我用google翻譯但是翻起來怪怪的看不太懂，不知道是否有高手可以解釋一下嘛?

With the shipping method you selected, there is no tracking information available. Your order shipped on April 11and is expected to reach your country within 15-30 business days once it clears customs and leaves the United States. This is only an estimate and does not include processing time at customs. 

If you do not receive your package by May 22, please let us know so we can begin an investigation. We will not be able to begin an investigation until that date. I appreciate your patience and understanding in this matter.